Events are yet another solution to communicate when asynchronous callbacks finish execution. An object can become emitter and publish events that other objects can listen to. This is one of the finest examples of the observer pattern.
The nature of this method is similar to "event listener", but much better than the latter because we can view the "message center" in order to find out how much signal is present and the number of subscribers for each signal, which runs the monitoring program.
The observer provides very loose coupling between objects. This provides the ability to broadcast changes to those who are listening to it. This broadcast may be for the single observer or a group of observers who are waiting to listen. The subject maintains a list of observers to whom it has to broadcast the updates. The subject also provides an interface for objects to register themselves. If they are not in the list, the subject doesn't...